1. Field of the Invention
The invention relates to an electronic module reader and, more particularly, to a system for detecting presence of a module in the reader and pre-warning regarding ejection of the module from the reader.
2. Brief Description of Prior Developments
Electronic module readers, such as a memory card readers for example, are provided in portable electronic devices, such as mobile telephones, digital cameras and hand-held games, for example. The readers allow a user to removably insert different modules for use by the device. In the past, the some readers were provided with a first switch for detecting the presence of a memory module in the reader. The reader could also have a separate second switch for signally a pre-warning if the module was being removed or ejected from the reader. This second switch was to allow for “hot swapping” of modules without having to turn OFF power to the device.
Referring to FIG. 1, there is shown a diagram of a conventional system used in a portable electronic device 10. The card reader 12 is coupled to a control system 14. The device includes a card detection switch 16 or card polling and a separate pre-warning switch 18, such as a reader door or hatch switch. The two switches 16, 18 are coupled to the control system for indicating presence of a memory card in the reader and a pre-warning to provide a certain time period to the control system before the memory card it removed. The switches 16, 18 have separate connections to the control system 14. The disadvantages with this type of system is increased difficulties in design, more space demanded because of a door switch, and higher probability of failures due to more connections and components.
One type of system uses a card detection switch which is closed at a mated position for an ON state, and which is open at a card ejected position for an OFF state. The switch contact is closed ON during operation which can cause poor reliability from bouncing and contact problems due to corrosion or mechanical reasons. Bouncing refers to inadvertent opening of a contact by impulse or momentum which could cause the contact to inadvertently switch from an ON state to an OFF state. This creates a reliability issue regarding the contact. A continuous closed ON state also can cause problems with corrosion and other reliability issues. Card ejection pre-warning time is only about 1 ms from switch detection to the moment the card is disconnected.
Another type of system uses a card detection switch which is open at a mated position for an OFF state, and which is open at a card ejected position for an OFF state. This can provide a longer ejection pre-warning time, but there is no card detection information when the card is IN or OUT of the reader because the status of the switch when mated and when OUT of the reader is OFF for both. Thus, it does not provide adequate card detection capability.
There is a desire to provide a reader having both a module detection capability as well as a pre-warning capability, but at a reduced cost. There is also a desire to provide a reader having both a module detection capability as well as a pre-warning capability with an increase reliability. There is a desire to provide a reader having both a module detection capability as well as a pre-warning capability, but with a smaller size and which is easier assembly than in conventional devices. There is also a desire to provide a reader which provides a minimum ejection pre-warning time of about 250 ms or more.